Method and system for improving provision of electrical stimulation

ABSTRACT

A method and system for providing stimulation to a user, the method including: transitioning a stimulation device from a baseline state to a first impedance monitoring state; during the first impedance monitoring state, guiding, an adjustment of a position of the stimulation device at a head region of the user to satisfy a first impedance criterion; upon satisfaction of the first impedance criterion, transitioning the stimulation device from the first impedance monitoring state to a stimulation regime that comprises a second monitoring state having a second criterion; upon detection of failure to satisfy the second criterion, transitioning the stimulation device from the stimulation regime to the first impedance monitoring state; and upon detecting that a third impedance criterion of the first impedance monitoring state is satisfied, transitioning the stimulation device from the first impedance monitoring state to the stimulation regime.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/426,212, filed 7, Feb. 2017, which claims the benefit of U.S.Provisional Application Ser. No. 62/292,511 filed 8, Feb. 2016 and U.S.Provisional Application Ser. No. 62/442,350 filed 4, Jan. 2017, whichare each incorporated in their entireties herein by this reference.

TECHNICAL FIELD

This invention relates generally to the neuromodulation field, and morespecifically to a new and useful method for improving provision ofelectrical stimulation.

BACKGROUND

Electrode systems in the neuromodulation field are used to transmitelectrical signals to a subject, and can be used to detect or measuresignals from the subject. Current electrode systems for electricalstimulation and/or signal detection are, however, insufficient for manyreasons including inadequate monitoring of stimulation-associatedparameters during stimulation, lack of safety features in a non-clinicalsetting, inadequate contact between the subject and the electrode(s) ofa system, inadequate notification and/or guidance of the subject whencontact is inadequate, non-robust contact between the subject and theelectrode(s) of a system, subject discomfort while using an electrodesystem, and/or limited use within multiple electrical simulation orbiosignal detection paradigms. Furthermore, methods of providingelectrical stimulation also fail to provide a positive user experience,fail to properly mitigate effects of voltage or current transients, andfail to provide control of other waveform aspects. As such, currentneuromodulation systems are inadequate for many reasons.

Thus, there is a need in the neuromodulation field for a new and usefulmethod and system for improving provision of electrical stimulation.This invention provides such a new and useful method and system.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts a schematic of an embodiment of a method for improvingprovision of electrical stimulation;

FIG. 2 depicts an example of impedance, current, and voltage behavior inan example of a method for improving provision of electricalstimulation;

FIG. 3 depicts an example current pulse output in an embodiment of amethod for improving provision of electrical stimulation;

FIG. 4 depicts variations of components implemented in a method forimproving provision of electrical stimulation;

FIG. 5 depicts an example of an application feature implemented in amethod for improving provision of electrical stimulation;

FIG. 6A depicts an embodiment of a system for improving provision ofelectrical stimulation;

FIG. 6B depicts examples of various system components in a system forimproving provision of electrical stimulation; and

FIGS. 7A-7B depict example electronics diagrams associated with a systemfor improving provision of electrical stimulation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of preferred embodiments of the invention isnot intended to limit the invention to these preferred embodiments, butrather to enable any person skilled in the art to make and use thisinvention.

1. Method

As shown in FIG. 1, an embodiment of a method 100 for providingelectrical simulation to a user comprises: upon activation of theelectrical stimulation device, transitioning the electrical stimulationdevice from a baseline state to a first impedance monitoring state S110;during the first impedance monitoring state, guiding, with thecontroller, an adjustment of a position of the electrical stimulationdevice at a body region of the user until a first impedance criterionassociated with the first impedance monitoring state is satisfied S120;upon satisfaction of the first impedance criterion, transitioning theelectrical stimulation device from the first impedance monitoring stateto a stimulation regime that comprises a second monitoring state havinga second criterion, wherein the stimulation regime provides anelectrical stimulation session, according to a set of waveform features,to the user S130; upon detection of failure to satisfy the secondcriterion, transitioning the electrical stimulation device from thestimulation regime to the first impedance monitoring state S140; andupon detecting that a third impedance criterion of the first impedancemonitoring state is satisfied, transitioning the electrical stimulationdevice from the first impedance monitoring state to the stimulationregime S150 (e.g., resuming the electrical stimulation session of BlockS130).

The method 100 functions to provide means for impedance monitoring inelectrical stimulation systems, with the goal of improving electricalstimulation treatment safety and/or efficacy. The method 100 can thusstrategically and automatically monitor provision of an electricalstimulation treatment delivered to a user as the user performs trainingactivities (e.g., athletic performance training, motor skills training,other training, other cognitive-associated tasks, etc.), wherein theelectrical stimulation treatment is provided within specified treatmentlimits (e.g., for safety, in consideration of maximizing efficacy of theelectrical stimulation treatment, etc.). However, the method 100 canadditionally or alternatively function to increase an effect of anelectrical stimulation treatment provided to the user or preemptivelywarn the user of conditions that might prevent the prescribed amount ofneurostimulation from being delivered, by ensuring that the impedanceparameters of the device-user body interface are within appropriateranges during the course of a stimulation treatment.

In other variations, the method 100 can be used to enhance effectivenessof electrical stimulation in coordination with a user performing a taskof interest, in order to enhance one or more of: motor ability (e.g.,dexterity, coordination), memory (e.g., working memory, declarativememory), cognitive ability (e.g., mathematical ability), learning (e.g.,language learning, speech learning), focus, attention, creativity,and/or any other suitable cognitive-associated attribute. In somespecific applications, the method 100 can be used to increase neuralplasticity in athletes who are attempting to improve performance inrelation to a set of skills. Additionally or alternatively, the method100 can be used to increase neural plasticity in stroke patients duringrehabilitation, to improve the efficacy of therapy sessions for patientswith paralyzing neurological disorders, and/or to increase neuralplasticity in elderly users.

Preferably, at least a portion of the method 100 is configured to beimplemented for a user who is outside of a clinical (e.g., hospital) orresearch (e.g., laboratory) setting, such that the user can be in anon-contrived environment as he or she is performing the set of tasksand/or receiving the electrical stimulation treatment. Additionally oralternatively, the method 100 can be implemented in an entirely clinicalor research setting, such as a physical therapy clinic.

The method can be implemented, at least in part, using a systemincluding an electrical stimulation device having a body-mountableportion and a set of electrodes coupled to the body-mountable portion,the electrical stimulation device operable between a baseline state, afirst impedance monitoring state, and a stimulation regime having asecond monitoring state, wherein the first impedance monitoring stateincludes a first set of impedance criteria and is enterable upon atleast one of: a) detection of activation of the electrical stimulationdevice and b) failure to satisfy an impedance criterion of the secondmonitoring state, during the stimulation regime, and wherein thestimulation regime provides a stimulation session with a waveformdefinition to the head region of the user upon satisfaction of at leastone of the first set of impedance criteria of the first impedancemonitoring state. The system can further include a controller thattransmits the stimulation waveform definition and guides adjustment ofthe set of electrodes at the head region of the user in cooperation withthe first impedance monitoring state.

As such, the method 100 can be implemented by a system that is portableand comfortably worn by the patient as the patient performs the set oftasks (e.g., athletic performance training tasks, memory improvingtasks, etc.). The method 100 can be implemented, at least in part, usingembodiments, variations, and examples of the systems described inSection 2 below and/or in U.S. application Ser. No. 14/470,683 titled“Electrode System for Electrical Stimulation” and filed on 27, Aug.2014, U.S. application Ser. No. 14/470,747 titled “Method and System forProviding Electrical Stimulation to a User”; U.S. App. No. 62/292,511titled “Stimulation System and Method” and filed on 8, Feb. 2016; U.S.App. No. 62/442,350 titled “Stimulation System and Method” and filed on4, Jan. 2017; U.S. application Ser. No. 14/878,647 titled “ElectrodeSystem for Electrical Stimulation” and filed on 8, Oct. 2015; U.S.application Ser. No. 15/059,095 titled “Method and System for ProvidingElectrical Stimulation to a User” and filed on 2, Mar. 2016; and U.S.application Ser. No. 15/335,240 titled “Electrode Positioning System andMethod” and filed on 26, Oct. 2016, which are each incorporated hereinin their entireties by this reference. The method 100 can, however, beimplemented using any other suitable stimulation system with acontroller (e.g., wearable stimulation system).

1.1 Method—Impedance Monitoring and Device Positioning

Block S110 recites: upon activation of the electrical stimulationdevice, transitioning the electrical stimulation device from a baselinestate to a first impedance monitoring state. Block S110 functions toprovide an initial regime of impedance checking when the electricalstimulation device is ready for use, in order to facilitate properpositioning of the device at the body region of the user in Block S120.

The electrical stimulation device of Block S110 preferably comprises anelectrical stimulation device including a head-mountable portion coupledeither reversibly or permanently to one or more electrodes, theelectrical stimulation device in communication with a controller (e.g.,a controller at least partially implemented using an applicationexecuting at a mobile computing device of the user). Embodiments,variations, and examples of a stimulation system are described in one ormore of U.S. application Ser. No. 14/470,683 titled “Electrode Systemfor Electrical Stimulation” and filed on 27, Aug. 2014, U.S. applicationSer. No. 14/470,747 titled “Method and System for Providing ElectricalStimulation to a User”; U.S. App. No. 62/292,511 titled “StimulationSystem and Method” and filed on 8, Feb. 2016; U.S. App. No. 62/442,350titled “Stimulation System and Method” and filed on 4, Jan. 2017; U.S.application Ser. No. 14/878,647 titled “Electrode System for ElectricalStimulation” and filed on 8, Oct. 2015; U.S. applicaion Ser. No.15/059,095 titled “Method and System for Providing ElectricalStimulation to a User” and filed on 2, Mar. 2016; and U.S. applicationSer. No. 15/335,240 titled “Electrode Positioning System and Method” andfiled on 26, Oct. 2016, which are each incorporated herein in theirentireties by this reference; however, the electrical stimulation devicecan additionally or alternatively include any other suitable electrodepositioning aspects and/or electrodes for providing stimulation. Forinstance, variations of the method 100 can be used for impedancemonitoring in any other electrical stimulation device for any othersuitable body region of a user, in relation to any other suitable typeof treatment.

The baseline state of the electrical stimulation device is preferably anon-stimulating state, or a state in which current through thestimulation path is below a threshold level for stimulation. Inexamples, the baseline state can be a deactivated state, a powered-offstate, an idling state, a standby state or any other suitable state.Transitioning from the baseline state to the first impedance monitoringstate can be triggered with transmission of the waveform definition forstimulation from the controller to the electrical stimulation device;however, transitioning from the baseline state to the first impedancemonitoring state (or any other state of the electrical stimulationdevice) can be triggered in any other suitable manner. In examples,transitioning from the baseline state can occur with any one or more of:receiving a user input (e.g., at the controller, at the device) to turnthe electrical stimulation device from a powered-off state to an activestate, receiving a user input (e.g., at the controller, at the device)to turn the electrical stimulation device from an idling state to anactive state, receiving a user input (e.g., at the controller, at thedevice) to turn the electrical stimulation device from a standby stateto an active state, detection of a change in the position of theelectrical stimulation device (e.g., from a resting position to aposition at the body of the user) with one or more motion sensors (e.g.,accelerometers, gyroscopes, image-based sensors, audio-based sensors,temperature-based sensors, force sensors, pressure sensors, etc.), andany other suitable trigger.

The first impedance monitoring state preferably provides monitoring ofimpedance along a path of stimulation, according to a waveformdefinition prescribed for the electrical stimulation session of BlockS130. As such, transitioning the electrical stimulation device from thebaseline state to the first impedance monitoring state can includeimplementing a path impedance operation that provides monitoring ofimpedance according to one or more criteria, along the stimulationpathway (e.g., in relation to different electrodes, in relation toelectrode regions, in relation to an interface between the electrode(s)and the body of the user, etc.). In addition to or in place ofmonitoring of impedance along a path of stimulation, the first impedancemonitoring state may provide monitoring of impedance through one or moreother paths, such as the set of paths in which each path is between twoadjacent electrical segments of a single physical electrode, or the setof paths in which each path is between one electrode and the combinedset of all other electrodes.

As shown in FIG. 2, in an example application of Block S110, uponactivation of the electrical stimulation device (e.g., turning thestimulation device on), a user can position a head-mountable portion ofthe electrical stimulation device (e.g., a headset) at his/her headregion, with electrodes of the head-mountable portion positionedapproximately near an intended position for stimulation. Prior toadjusting the position of the electrodes coupled to the head-mountableportion, impedance (R) through the stimulation path to the user may behigh. In the example, activation of the electrical stimulation deviceincludes transmission of a waveform definition from the controller tothe electrical stimulation device, which governs the electricalstimulation session described in examples of Block S130. In the example,after transmission of the waveform definition, the controller commandsthe electrical stimulation device to initiate measurement of impedancealong a path according to the waveform definition, according to a pathimpedance monitoring operation. However, alternative examples of BlockS1 io can be implemented in any other suitable manner. For example,prior to adjusting the position of the electrodes coupled to thehead-mountable portion, impedance (R) through the stimulation path tothe user may be low, where this low impedance indicates that theposition of the electrodes is not optimal (e.g. the electrodes are tooclose to each other or are shorted together). In another example, priorto adjusting the position of the electrodes coupled to thehead-mountable portion, the complex impedance (Z, not shown) orfrequency-dependent complex impedance (Z(f), not shown) through thestimulation path may not fall within a desirable range (e.g. a rangethat indicates that the electrodes are making contact with a correctanatomical region of the head, based on comparison with known electricalimpedance tomology and/or electrical impedance plethysmographic data; arange that indicates that the size or electrical properties of theelectrode-tissue interface are desirable for beginning stimulation). Ingeneral, the use of impedance herein may alternatively or additionallyinclude complex impedance or frequency-dependent complex impedance inaddition to conventional resistance. This complex impedance may bemeasured using techniques such as delivery of sinusoidal waveforms atvarying or superimposed frequencies, or by extraction of compleximpedance information from the shape of voltage transients produced bydelivery of current pulses.

Block S120 recites: during the first impedance monitoring state,guiding, with the controller, an adjustment of a position of theelectrical stimulation device at a body region of the user until a firstimpedance criterion associated with the first impedance monitoring stateis satisfied. Block S120 functions to coordinate impedance monitoringwith readjustment of the electrical stimulation device until impedancealong the stimulation path is low enough to improve chances of having anon-disrupted stimulation session in Block S130.

In coordination with adjustment of the position of the electricalstimulation device at the body of the user, Block S120 can includeoutputting, through the electrical stimulation device, one or morecurrent pulses, during which voltage parameters and/or currentparameters can be monitored to determine impedance along the stimulationpath(s). Block S120 preferably includes outputting a set of currentpulses throughout the adjustment period, but can alternatively includeoutputting a single current pulse during the readjustment period.Alternatively, the outputted pulses can be voltage pulses, during whichcurrent parameters and/or voltage parameters can be monitored todetermine impedance along the stimulation path(s).

In variations wherein a set of current pulses is output by theelectrical stimulation device, the set of current pulses can includepulses having uniform pulse width, or can alternatively include pulseshaving non-uniform pulse widths (e.g., one or more pulses can have awidth different than other pulses in the set of current pulses.Additionally or alternatively, each pulse in the set of pulses can havean identical amplitude to other pulses in the set of pulses (e.g., 0.18mA zero-to-peak amplitude, zero-to-peak amplitude from 0.01 mA to 0.50mA, etc.), or can alternatively, one or more pulses in the set of pulsescan have a non-identical amplitude to other pulses in the set of pulses.The set of current pulses can additionally or alternatively be providedat a constant frequency (e.g., with constant time spacing betweenpulses, at a frequency between 2 and 20 Hz, etc.), or can alternativelybe provided with non-uniform time spacing between pulses (e.g., randomtime spacing between pulses). Still alternatively, current pulses can beoutput whenever a sensor (e.g., accelerometer, gyroscope, magnetometer,force sensor, etc.) of the electrical stimulation device detects achange in position of the electrical stimulation device during the firstimpedance monitoring state. For instance, a current pulse or set ofcurrent pulses can be output after each of a set of adjustments to theposition of the electrical stimulation device, detected by way of anabove threshold motion of the electrical stimulation device detectedusing accelerometers. However, the set of current pulses can be outputin any other suitable manner.

The set of current pulses preferably comprise biphasic current pulses,an example of which is shown in FIG. 3, in order to avoid bias inimpedance measurements produced using constant currents or monophasicpulses, and/or to facilitate controlled studies using sham electricalstimulation consisting at least in part of simulated stimulation whoseactual amplitude is zero or very low, during which impedance andproblems with electrode position must be detected in a realistic manner,embodiments, variations, and examples of which are described in U.S.application Ser. No. 14/470,683 titled “Electrode System for ElectricalStimulation”. However, the set of current pulses can additionally oralternatively include one or more monophasic pulses, pseudomonophasicpulses, or pulses having alternative shapes.

In using biphasic current pulses, the set of pulses can include biphasicpulses including interphase intervals, or can include biphasic pulseswithout interphase intervals. During an interphase interval, theelectrodes may optionally be shorted together internal to the device.Furthermore, the biphasic pulses can have a square-wave profile, anexample of which is shown in FIG. 3. However, other variations, thebiphasic pulses can have any other suitable profile (e.g., sawtoothprofile, etc.).

In variations, implementing the first impedance monitoring state caninclude implementing elements (e.g., components in software, componentsin hardware, components in firmware) for management of one or moredigital-to-analog converters (DACs) of the electrical stimulationdevice, wherein the DACs transform a digital waveform definition fromthe controller to an analog output (e.g., to an output stage thatcomprises a voltage-controlled current source including an amplifieroperable to take an input voltage from the DAC and produce a controlledcurrent through the stimulation path in proportion to the input voltage,to the electrodes of the electrical stimulation device used forstimulation). As such, as shown in FIG. 4, one or more of Blocks S110and S120 can include implementing a first DAC management component thatproduces the set of current pulses for impedance monitoring as describedabove. In variations, the first DAC management component can beimplemented in software and produce biphasic pulses whenever a portionof the waveform definition (or impedance monitoring state) has a valuebelow a threshold current value, such that impedance through thestimulation path(s) can be checked (e.g., using total peak-to-peakvoltage divided by total peak-to-peak current) even when current outputis low. In a specific example, the current threshold is 0.3 mA, suchthat the first DAC management component with the DAC governs/controlsoutput of biphasic current pulses whenever the current output is below0.3 mA; however, in variations of the specific example, the currentthreshold for the first DAC management component can have any othersuitable current value or range of values (e.g., from 0 mA to 1 mA,etc.). In variations, the DAC and output stage are both only capable ofgenerating monophasic or substantially monophasic pulses, and/or outputof a single polarity or of substantially a single polarity; in thesevariations, a biphasic output current pulse can be generated by use ofmultiplexing switches positioned functionally between the output stageand the user, such that the polarity is switched between the leadingphase and the trailing phase.

As such, in examples of Block S110, biphasic current pulses are outputduring the first impedance monitoring state whenever the amount ofcurrent that is delivered through the stimulation pathway (e.g. asspecified by a waveform definition), is below a threshold amount ofcurrent; however, the set of current pulses can additionally oralternatively be delivered in any other suitable manner.

The first impedance criterion of the first impedance monitoring state ispreferably an impedance or resistance-based criterion that involvesmeasurement of impedance in non-stimulating regimes of the electricalstimulation device. In one variation, impedance can be determined as atotal peak-to-peak voltage measured during a biphasic pulse divided by atotal peak-to-peak current output during the biphasic pulse. In anothervariation, impedance/resistance can be measured in any other suitablemanner.

In still other variations, impedance can alternatively be indirectlyinferred based upon the amount of current that can actually be deliveredthrough the stimulation path(s). However, impedance monitoring can beimplemented in another manner in Block S120.

The first impedance criterion is preferably more stringent than thethird impedance criterion used in Block S150, as described in moredetail below, in order to provide more stringent requirements forinitializing stimulation, in comparison to re-initializing stimulationif, for some reason, impedance increases above a threshold limit duringthe stimulation regime. In practice, greater stringency in the firstimpedance criterion, as compared to the third impedance criterion, canbe based upon difficulty of achieving the impedance criterions. Forinstance, because impedance may drop after the initial onset ofstimulation, setting the same impedance threshold for both the firstimpedance criterion and the third impedance criterion produces an easierto achieve third impedance criterion (i.e., after the stimulationsession has begun or progressed). However, the first impedance criterioncan alternatively be identical to the third impedance criterion of BlockS150, or can alternatively be less stringent than the third impedancecriterion of Block S150. For instance, the device can be configured suchthat prior to entering the stimulation regime of Block S130, themeasured impedance must be below a threshold limit of 10 kΩ (e.g., afirst impedance criterion), but after stimulation has been interruptedin Block S140, re-initializing stimulation can occur when the measuredimpedance is below a threshold limit of 12 kΩ (e.g., a third impedancecriterion). However, the first impedance criterion and the thirdimpedance criterion can additionally or alternatively have any othersuitable impedance threshold values (e.g., 1 kΩ, 5 kΩ, 10 kΩ, 15 kΩ,etc.) or any other suitable range of threshold conditions for impedance(e.g., 5-10 kΩ, 8-12 kΩ, etc.)

In relation to guiding the adjustment of the position of the electricalstimulation device at the body of the user in Block S120, Block S120 caninclude guiding the user to manually position the electrical stimulationdevice using one or more of: visual guidance, auditory guidance, hapticguidance, and any other suitable form of guidance. In a first variation,a display of the controller (e.g., a display of a mobile computingdevice along with an application executing at the mobile computingdevice) can be configured to provide live guidance for dynamicallyadjusting the position of the electrical stimulation device, examples ofwhich are shown in FIG. 5. Additionally or alternatively, in anothervariation, wherein the electrical stimulation device comprises a headsetthat positions electrodes at the head of the user, audio output devices(e.g., beeping elements, speaker elements, etc.) coupled to the headsetcan be configured to provide guidance in relation to positioning of theheadset. In a first example, one or more of beeping frequency, pitch,and loudness, or vibration frequency or amplitude, can be reduced as theheadset approaches an optimized position. In another example, verbalinstructions can be delivered through speakers of the headset. However,guidance for manual adjustment can be provided in Block S120 in anyother suitable manner.

Alternatively, Block S120 can additionally or alternatively includeautomatic adjustment of the electrical stimulation device to providesuitable impedance through the stimulation path(s) to initializestimulation in Block S130. In one such example, Block S120 can includeimplementing vibration motors (e.g., eccentric rotating mass devices)operable to vibrate the electrical stimulation device (e.g., a headsetportion of the electrical stimulation device) at the body of the useruntil the first impedance criterion is achieved. However, automaticadjustment of the position of the electrical stimulation device can beachieved in Block S120 in any other suitable manner.

As shown in FIG. 2, in an example application of Block S120, once a pathimpedance operation has been initiated (in the example of Block S110above), the electrical stimulation device can be configured to producebiphasic current pulses, in coordination with measurement of impedanceby the electrical stimulation device, wherein the impedance is measuredby dividing the total peak-to-peak voltage measured during a biphasicpulse by the total peak-to-peak current output during the biphasicpulse. The example application thus allows for collection of ahigh-quality impedance measurement, even if interfaces involving theelectrode (e.g., an electrode-to-tissue interface, anelectrode-to-saline interface, etc.) develop electrochemical potentialsthat could otherwise affect impedance determination. The example ofBlock S120 described thus implements an impedance/resistance-focusedcriterion, rather than a current-focused criterion associated with howmuch current can actually be delivered through the stimulation pathway.

In the example application of Block S120 above, and concurrent with thebiphasic pulse-based impedance measurements, the example can furtherinclude guiding the user, within an application executing at the mobilecomputing device of the user (i.e., the controller), to adjust theposition of a head-mountable portion of the electrical stimulationdevice until contact between electrodes coupled to the head-mountableportion and the user's head is improved. Guiding, in the example, caninclude rendering a representation of the head-mountable portion of theelectrical stimulation device along with representations of electrodesrelative to the head-mountable portion, with indications of whichelectrodes have poor contact, an example of which is shown in FIG. 5.Upon achieving an impedance value lower than a threshold impedance value(e.g., 16 kΩ, 5-25 kΩ, etc.) the example application of the method 100can include transitioning the electrical stimulation device from thefirst impedance monitoring state to the stimulation regime, as describedin relation to Block S130 below. However, alternative examples of BlockS120 can implement any other suitable impedance criterion forinitializing stimulation according to Block S130, or otherwise beimplemented in any other suitable manner. In an example, the impedancecriterion of Block S120 and/or other impedance criteria described hereinmay also be implemented as two-part criteria involving hysteresis, inorder to reduce rapid cycling between an impedance monitoring state andan electrical stimulation regime. For example, the impedance criterioncould require that impedance initially fall below an initial threshold,such as 15 kΩ, however briefly, but remain under a somewhat higherthreshold, such as 20 kΩ, for a duration such as five seconds in orderto exit the impedance monitoring state.

1.2 Method—Stimulation and Impedance Monitoring

Block S130 recites: upon satisfaction of the first impedance criterion,transitioning the electrical stimulation device from the first impedancemonitoring state to a stimulation regime that comprises a secondmonitoring state having a second criterion, wherein the stimulationregime provides an electrical stimulation session, according to a set ofwaveform features, to the user. Block S130 functions to initiate andprovide a session of stimulation, once impedance along the stimulationpath(s) is suitable according to Blocks S110 and S120.

Transitioning the electrical stimulation device to the stimulationregime preferably includes implementing a stimulation session accordingto the waveform definition transmitted to the electrical stimulationdevice by the controller.

In variations, implementing the stimulation session according to thewaveform definition can include implementing elements (e.g., componentsin software, components in hardware, components in firmware) formanagement of one or more digital-to-analog converters (DACs) of theelectrical stimulation device, wherein the DACs transform a digitalwaveform definition from the controller to an analog output (e.g., to anoutput stage that comprises a voltage-controlled current sourceincluding an amplifier operable to take an input voltage from the DACand produce a controlled current through the stimulation path inproportion to the input voltage, to the electrodes of the electricalstimulation device used for stimulation).

As such, as shown in FIG. 4, Block S130 can include implementing asecond DAC management component that modulates waveform componentsinvolving abrupt transitions in current output (e.g., abrupt transitionsfrom a high current state to a low current state or from a low currentstate to a high current state), in order to improve user comfortassociated with the electrical stimulation provided. The second DACmanagement component thus ramps down current and/or ramps up currentaccording to a desired ramp rate, for features of the waveformdefinition that have an above threshold change (e.g., a maximum stepvalue) in current value. In an example, the second DAC managementcomponent is implemented as a software object that tracks step changesin current delivered and, if a step change in current is detected, thesecond DAC management component transforms the step change into anappropriate ramped up or ramped down change in current, in order toenhance user comfort.

The threshold change in current that triggers current ramping by thesecond DAC management component can be a fixed threshold across multipleusers, or can alternatively be user-specific or demographic specific.For instance, in an example, the threshold change in current beforeramping occurs can be set by a user during calibration of the electricalstimulation device, wherein the user can experience different stepchanges in current and indicate the step size at which discomfortbegins. In another example, biological parameters of the user (e.g.,skin thickness, touch receptor distribution, etc.) can be used todetermine an appropriate threshold value. In another example, thethreshold change in current before ramping occurs could be set by thewaveform definition, and/or modified during the course of waveformdelivery by data in the waveform definition. However, the thresholdchange can alternatively be determined in any other suitable manner.

In variations of the second DAC management component, the ramp rate canbe constant regardless of the current step size. Alternatively, the ramprate parameters can depend upon the current step size (e.g., an inverserelationship can exist between step size and ramp rate). Furthermore,the ramp rate for ramping up current can be the same as or differentfrom the ramp rate for ramping down current. Additionally oralternatively, the ramp can include a linear ramp or a non-linear ramp.However, transforming a waveform definition by the second DAC managementcomponent can alternatively be implemented in any other suitable manner.

Additionally or alternatively, the second DAC management component canmodulate waveform components including abrupt transitions from a statewhere the current waveform is of low energy (e.g., zero output, or anoscillatory waveform of RMS value 0.1 mA) to a state where the currentwaveform is of high energy (e.g., an oscillatory waveform of RMS value1.0 mA), or vice-versa from high energy to low energy. This embodimentof the second DAC management component thus ramps down overall scaling,energy, or RMS value of the delivered waveform and/or ramps up overallscaling, energy, or RMS value of the delivered waveform according to adesired ramp rate.

Additionally or alternatively, a third DAC management component, asshown in FIG. 4, can be included in the system of Block S130, in orderto deliver sham stimulation in the course of e.g. a clinical trial. Thisthird DAC management component can act to divert stimulation currentthrough an internal shorted path, or to replace the stimulation outputprescribed by the waveform definition with a zero-amplitude orlow-amplitude sham output while simultaneously collecting impedance dataand producing realistic system behavior such as alerting the user ifconnection to the head is lost. This third DAC management component canbe enabled by the user, or remotely, or may be enabled and disabled bydata contained within the waveform definition. Additionally oralternatively, a fourth DAC management component, as shown in FIG. 4,can be included in the system of Block S130, in order to scalestimulation output according to user input. This scaling may beaccomplished e.g. by applying a predefined multiplier or a multiplierspecified by the waveform definition to the DAC output for each of a setof amplitude levels selectable by the user (e.g., using a knob or slidercontrol element on a user interface on a controller 220), embodiments,variations, and examples of which are described in U.S. application Ser.No. 15/059,095 filed 2, Mar. 2016, which is herein incorporated in itsentirety by this reference.

The stimulation session of the stimulation regime is preferablyimplemented using electrodes wetted with saline; however, thestimulation session of the stimulation regime can alternatively beimplemented using any other suitable type(s) of electrodes. Inembodiments, variations, and examples, stimulation is carried out usingelectrodes as described in one or more of: U.S. application Ser. No.14/470,683 titled “Electrode System for Electrical Stimulation” andfiled on 27, Aug. 2014; U.S. application Ser. No. 14/470,747 titled“Method and System for Providing Electrical Stimulation to a User”; U.S.App. No. 62/292,511 titled “Stimulation System and Method” and filed on8, Feb. 2016; U.S. App. No. 62/442,350 titled “Stimulation System andMethod” and filed on 4, Jan. 2017; U.S. application Ser. No. 14/878,647titled “Electrode System for Electrical Stimulation” and filed on 8,Oct. 2015; U.S. application Ser. No. 15/059,095 titled “Method andSystem for Providing Electrical Stimulation to a User” and filed on 2,Mar. 2016; and U.S. application Ser. No. 15/335,240 titled “ElectrodePositioning System and Method” and filed on 26, Oct. 2016; however,Block S130 can additionally or alternatively implement any othersuitable electrode system, or any system of transducers such asultrasound or light-emitting elements for brain stimulation.

The stimulation session of the stimulation regime of Block S130preferably includes transcranial electrical stimulation (TES) configuredto stimulate a brain region of the user in the form of at least one of:transcranial direct current stimulation (tDCS), transcranial alternatingcurrent stimulation (tACS), transcranial magnetic stimulation (TMS),transcranial random noise stimulation (tRNS), transcranial variablefrequency stimulation (tVFS), and any other suitable form oftranscranial stimulation.

In variations the waveform of the stimulation regime of Block S130 canbe associated with one or more of: direct current (DC) stimulation;alternating current (AC) stimulation; pulse trains, random stimulation;pseudorandom stimulation; substantially pseudorandom noise stimulation;band-limited random noise stimulation; band-limited pseudorandom noisestimulation; variable frequency stimulation (VFS); stimulation withcomposite superposed waveforms; and any other suitable type ofstimulation. The waveform(s) of the stimulation can be defined byparameters including one or more of: amplitude, frequency, spectrum,pulse width, inter-pulse interval, and any other suitable parameters,wherein the parameter(s) are constant over at least a portion of thewaveform. Additionally or alternatively, in some variations of BlockS130, the parameter(s) of the waveform can vary over at least a portionof the waveform. However, Block S130 can include providing stimulationtreatment with any other suitable type of waveform, embodiments,variations, and examples of which are described in U.S. application Ser.No. 14/470,747 titled “Method and System for Providing ElectricalStimulation to a User”.

The stimulation session of the stimulation regime of Block S130 canadditionally or alternatively implement method steps for waveformtransformation, embodiments, variations, and examples of which aredescribed in U.S. application Ser. No. 15/059,095 titled “Method andSystem for Providing Electrical Stimulation to a User” and filed on 2,Mar. 2016. However, the stimulation session of the stimulation regime ofBlock S130 can additionally or alternatively be implemented in any othersuitable manner.

In relation to the second monitoring state of Block S130, the secondcriterion can include a current-focused criterion. In one variation, thecurrent-focused criterion can measure impedance by dividing actualstimulation voltage (V) by actual stimulation current (i_(actual)). Inanother variation, the current-focused criterion can include monitoringof a difference between the current that is attempted to be delivered(i_(attempted)), and the actual current (i_(actual)) that is delivered.In specific examples, the difference threshold can be an absolutedifference or can alternatively be a percent difference (e.g., 10%difference between i_(actual) and i_(attempted)), or can be defined asthe larger of a percent difference and an absolute difference (e.g., 10%or 0.1 mA difference, whichever is greater). As such, the secondcriterion can be associated with a determination of how much current canactually be delivered in a specific configuration of the electricalstimulation device at the body of the user. In this variation, if theactual current (i_(actual)) less than the current that is attempted tobe delivered is (i_(attempted)) by an above-threshold amount, the secondcriterion is not satisfied and Block S140 is implemented. However, aslong as the current that is attempted to be delivered (i_(attempted)) iswithin a threshold range of the actual current (i_(actual)) that isdelivered, the second criterion is satisfied and the stimulation sessionof the stimulation regime of Block S130 continues. The second impedancecan additionally or alternatively have a duration factor (e.g., animpedance or current threshold condition must be sustained for a certainperiod of time before stimulation is paused, or must be observed for acertain number of measurements in a certain time window); however, thesecond monitoring criterion (and/or the first impedance monitoringcriterion) can additionally or alternatively have any other suitableconditions.

Additionally or alternatively, the stimulation regime of Block S130 canimplement the first DAC management component to produce biphasic currentpulses (or other current pulses) for impedance measurements (e.g., inlow current portions of the waveform definition, etc.).

Additionally or alternatively, in relation to safety, the method and/orsystem described can implement a multiplexer (MUX) array with a set ofinternal switches (e.g., an analog switch solid state relay) configuredto pass desired current outputs to electrodes for stimulation, and toshort/route undesired current back to the system. As such, transients,anomalies, and/or undesired high currents can be safely routed throughalternative pathways and away from the electrodes for stimulation, toprotect the user from unsafe currents; for instance, if the systemdetects that the delivered current is higher than the current specifiedby the waveform definition by a given threshold, the system can react byshorting all outputs together, ensuring that no current reaches theuser, while additionally alerting the user.

As shown in FIG. 2, in an example application of Block S130, once thecontroller of the system determines that the first impedance criterionhas been satisfied (e.g., by comparing impedance to a threshold, byrequiring that the threshold condition has not been satisfied for acertain duration of time), the controller can issue a command totransition from the first impedance monitoring state and to initializethe stimulation regime. In the specific example, the stimulation sessionincludes a waveform definition component of direct current (DC)stimulation at a specific level, and because the DC level is above athreshold amount, the second DAC management component of the specificexample implements a linear ramp to the DC level for user comfort. Inthe specific example, as the current is ramped to the DC level, thefirst DAC management component of the specific example produces biphasicpulses when the delivered current is below a current threshold (e.g.,0.3 mA) in order to provide accurate impedance measurements, but abovethe threshold current, impedance is measured by dividing actualstimulation voltage by actual stimulation current delivered. Oncestimulation has started in the stimulation regime, measured impedancetypically (but not necessarily) rises to a higher value over a shortperiod of time due to electrochemical reactions at theelectrode-to-tissue interface, and then typically (but not necessarily)drops gradually over the course of stimulation over a longer period oftime (e.g., due to electrochemical reactions and biological effects,such as poration or vasodilation of tissue proximal to the electrodes),as shown in FIG. 3. However, variations of the specific example of BlockS130 can operate in any other suitable manner or produce any othersuitable behavior.

1.3 Method—Impedance Change Detection and Device Re-Adjustment

Block S140 recites: upon detection of failure to satisfy the secondcriterion, transitioning the electrical stimulation device from thestimulation regime to the first impedance monitoring state. Block S140functions to stop stimulation or otherwise stop attempts to output acurrent for stimulation if current (e.g., in relation to measuringattempted vs. actual current) or impedance do not satisfy desiredthreshold criteria.

In Block S140, determining that the second criterion has not beensatisfied can include: comparing actual current, i_(actual), beingdelivered to attempted current, i_(attempted), delivered andtransitioning to the first impedance monitoring state if the differencebetween i_(actual) and i_(attempted) is above a threshold (e.g., athreshold percent difference, a threshold absolute difference, etc.).Additionally or alternatively, determining that the second criterion hasnot been satisfied can include determining impedance by dividing actualvoltage by actual current, and transitioning to the first impedancemonitoring state if the impedance is greater than a threshold impedancevalue. However, determining that the second criterion has not beensatisfied can be performed in any other suitable manner.

In variations, failure to satisfy the second criterion can occur due tosituations including one or more of: motion of the user during strenuousactivity (e.g., performance of an athletic training regimen whilecoupled to the electrical stimulation device); motion of the user duringnon-strenuous activities (e.g., the electrical stimulation device slipsfrom a position as the user moves about during a non-strenuousactivity); removal of the electrical stimulation device (e.g., by theuser, by another entity) due to discomfort during stimulation; removalof the electrical stimulation device (e.g., by the user, by anotherentity) due to intentions to prematurely stop stimulation;impedance-related failures due to electrode fouling; impedance-relatedfailures due to electrode saturation state (e.g., by saline, etc,including increase of impedance due to drying.); impedance-relatedfailures due to improper coupling between the electrodes and otherportions of the electrical stimulation device; impedance-relatedfailures due to system electrical system failure; and any other suitablesituation that results in unsuitable impedance characteristics along thestimulation path(s).

Transitioning the electrical stimulation device from the stimulationregime to the first impedance monitoring state in Block S140 preferablyincludes implementing the second DAC management component described inBlock S130 above, whereby the second DAC management componentappropriately ramps the stimulation current down to below a thresholdcurrent level associated with the first impedance monitoring state. Inthis variation, ramping down the current promotes user comfort, suchthat jarring changes in current experienced at the electrode-tissueinterface are not provided to the user. However, Block S140 canalternatively omit ramping down the current by way of a second DACmanagement component.

Additionally or alternatively, in relation to transitioning to the firstimpedance monitoring state, Block S140 can include implementing thefirst DAC management component to produce a set of current pulses fordetermining impedance in a low current state (or zero current state) ofthe electrical stimulation device. Similar to Block S110 above, thefirst DAC management component, with the DAC, can be configured toprovide biphasic pulses with an optional interphase interval at a setfrequency when the current drops below a threshold current limit, duringthe transition from the stimulation regime to the first impedancemonitoring state. However, Block S140 can alternatively omitimplementation of the first DAC management component and can operate inany other suitable manner.

Similar to Block S110 above, once the first impedance monitoring statehas been arrived at (or prior to arrival at the first impedancemonitoring state), the controller and/or the electrical stimulationdevice can be configured to guide adjustment of the electricalstimulation device at the body region of the user until proper impedancecharacteristics along the stimulation path(s) are achieved, similar tomethods described in Blocks S110 and S120. However, guidance foradjusting the electrical stimulation device at the body region of theuser can alternatively be implemented in any other suitable manner.

As shown in FIG. 2, in an example application of Block S140, once ahead-mountable portion of the electrical stimulation device begins tolose contact with the head of the user (e.g., due to strenuousactivity), impedance begins to rise to a level at which the voltageavailable to the output stage (to the electrodes) is insufficient todrive the attempted current, i_(attemped), through the stimulationpath(s), and the actual current, i_(actual), delivered deviates from theattempted current, i_(attempted). This condition is detected by theelectrical stimulation device, which implements the second criterion byperiodically monitoring (e.g., 10 times per second, once per second,etc.) and comparing i_(attemped) to i_(actual) and providing a currenterror output if i_(attemped) and i_(actual) differ by a threshold amount(e.g., 10%, 0.1 mA, any percent difference from 1-20%, any currentdifference from 0.02-0.5 mA, etc.), with a threshold frequency (e.g.,i_(attemped) and i_(actual) are significantly different for 30% ofmeasurements within a given 1-second window), or with a threshold numberof sequential instances (e.g., 3 sequential differences betweeni_(attemped) and i_(actual)).

As such, in the example of Block S140, when the current deviation isdetected, the electrical stimulation device begins to ramp down thestimulation current according to a programmed maximum ramp slope (e.g.,0.3 mA per second) to transition from the stimulation regime to thefirst impedance monitoring state. Similar to the example described inrelation to Blocks S110 and S120, the electrical stimulation device thenbegins providing biphasic current pulses, and the user is prompted toadjust position of the head mountable portion of the electricalstimulation device in manners similar to that described in Blocks S110and S120 above.

In the example of Block S140 above, one or more of the electricalstimulation device and the controller can be configured to output one ormore error notifications (e.g., visually with displays or light,haptically, audibly, etc.). For instance, one or more of the electricalstimulation device and the controller can provide a status condition oran error notification upon transition from the stimulation regime to thefirst impedance monitoring state. Additionally or alternatively, one ormore of the electrical stimulation device and the controller can providea status condition or an error notification if a parameter of thecurrent delivered was too high (e.g., with no option to continue orrestart stimulation). Additionally or alternatively, one or more of theelectrical stimulation device and the controller can provide a statuscondition or an error notification if a parameter of the currentdelivered was too low (e.g., if the head-mountable portion of theelectrical stimulation device loses contact with the head of the user).However, any other suitable status condition or error notification canbe provided.

1.4 Method—Transitioning to Stimulation

Block S150 recites: upon detecting that a third impedance criterion ofthe first impedance monitoring state is satisfied, transitioning theelectrical stimulation device from the first impedance monitoring stateto the electrical stimulation regime. Block S150 functions to transitionthe electrical stimulation device back to the stimulation regime (oranother appropriate state of the electrical stimulation device), oncethe impedance characteristics for the stimulation path(s) are below agiven threshold for stimulation to begin.

In some variations, implementation of the first impedance monitoringstate in Block S150 is similar to implementation of the first impedancemonitoring state in Block S120. However, as indicated in Block S120above, the third impedance criterion is preferably different from thefirst impedance criterion of Block S120. In one variation, the thirdimpedance criterion is less stringent than the first impedancecriterion, in order to provide more stringent requirements forinitializing stimulation, in comparison to re-initializing stimulationafter impedance increases above a threshold limit during the stimulationregime (e.g., due to lost contact during strenuous activity). Again, inpractice, greater stringency in the first impedance criterion, ascompared to the third impedance criterion, can be based upon difficultyof achieving the impedance criterions. For instance, because impedancemay drop after the initial onset of stimulation, setting the sameimpedance threshold for both the first impedance criterion and the thirdimpedance criterion produces an easier to achieve third impedancecriterion (i.e., after the stimulation session has begun or progressed).In an example, the third impedance criterion and the first impedancecriterion can each have an associated impedance threshold of 10 kΩ,given that it is easier to achieve 10 kΩ in impedance once stimulationhas begun or progressed. In another example, the third impedancecriterion can have an associated impedance threshold of 12 kΩ toreinitialize stimulation, in comparison to a first impedance thresholdof 10 kΩ required to start a new stimulation session. However, asindicated above, each of the first impedance criterion and the thirdimpedance criterion can include a range of impedance values for startingstimulation (e.g., the first impedance criterion can have an associatedrange of 5-10 kΩ and the third impedance criterion can have anassociated range of 8-13 kΩ). Similar to the criteria described in BlockS120 above, the impedance criterion of Block S150 can have a factorassociated with duration or number of pulses. For instance, in a firstexample, the third impedance criterion can require that impedanceremains below a threshold value for 5 seconds before stimulationre-initializes. In a second example, the third impedance criterion canrequire that impedance remains below a threshold value for 10 biphasicpulses. However, the third impedance criterion can additionally oralternatively have any other suitable conditions to provide properperformance of the electrical stimulation device and/or to enhance usersafety.

Furthermore, the third impedance criterion can alternatively beidentical to the first impedance criterion of Block S120, or canalternatively be more stringent than the first impedance criterion ofBlock S120.

Any one or more of the above Blocks, in relation to implementing thefirst impedance monitoring state, providing stimulation, monitoringimpedance/current, leaving the stimulation regime, re-implementing thefirst impedance monitoring state, and/or re-entering the stimulationregime, can be implemented with involvement of the controller, orindependently of the controller (e.g., at a head mountable portion ofthe electrical stimulation device). For instance, the method 100 can beimplemented for a user who has placed the controller (e.g., a mobiledevice executing an application and, in some circumstances, incommunication with the head mountable portion of the electricalstimulation device) at a remote location while performing a trainingactivity with the head mountable portion of the electrical stimulationdevice. However, the method 100 can additionally or alternatively beimplemented in any other suitable manner.

In relation to transitioning the electrical stimulation device to theelectrical stimulation regime, Block S150 can include simply resumingthe stimulation session at the point at which the stimulation sessionstopped in Block S140. Alternatively, Block S150 can include continuingstimulation according to a modified stimulation session, based on one ormore factors including: duration of time for which stimulation was notprovided to the user during Block S140; cause of high impedance;attempted current output before transitioning to the first monitoringstate from the stimulation regime; user intentions (e.g., the user maynot want to continue stimulation); amount of stimulation that the userhas received in a given time period; detection of biometric parametersof the user (e.g., in relation to cardiovascular parameters, in relationto neurological parameters, in relation to respiratory parameters, inrelation to parameters indicative of stress, etc.); and any othersuitable factors.

For instance, in a first example, if the user's stimulation session hasonly been interrupted for below a threshold duration of time (e.g., 30seconds), the stimulation session can resume at the point at which thestimulation session stopped in Block S140. Additionally oralternatively, if the user's stimulation session has been interruptedfor above a threshold duration of time (e.g., 10 minutes), thestimulation session can be resumed with modifications (e.g., stimulationcan be resumed at a time point before the point at which stimulation wasinterrupted, stimulation can be resumed with changes inintensity/amplitude, etc.). Additionally or alternatively, if the user'sstimulation session was interrupted near the end of the stimulationsession, the stimulation session may not be resumed because the desiredeffectiveness has been nearly achieved.

For instance, in some applications, it may be desirable that anaggregated amount of at least one stimulation parameter of thestimulation session provided during a time window does not exceed amaximum limit, for example, for safety reasons. As such, a maximum limitfor an aggregated value of a stimulation parameter as related to BlocksS130-S150 can be any one or more of: a maximum dosage (e.g., duration ofstimulation, aggregated charge, aggregated charge density, etc.) perday, a maximum dosage per shorter unit of time (e.g., minutes, hours),and any other suitable maximum dosage. In one example, a daily dosage of30 minutes is an acceptable dosage of tDCS, with higher doses increasingchances of skin irritation for the user and/or other side effects.Furthermore, a remaining allowable stimulation can be tracked inrelation to the maximum limit as an accumulated amount of stimulationsubtracted from a maximum dosage of stimulation. Here, the accumulateddosage can be increased by additional electrical stimulation, anddecreased (e.g., according to a logarithmic decay) when stimulation isnot occurring. Thus, maximizing an effect of electrical stimulationtreatment given a maximum acceptable limit of treatment cansignificantly benefit a user'srecovery/rehabilitation/learning/improvement rate. In variations whereinthe electrical stimulation treatment includes TES, the maximum limit ispreferably a maximum amount of charge or charge density (e.g.,determined based upon current amplitude, duration, duty cycle, andelectrode path) that can be delivered to the user per unit time (e.g.,the time window), or a maximum amount of total charge (e.g., currentmultiplied by total delivery time). Additionally or alternatively, theelectrical stimulation provided within the time window can betransmitted and modulated such that at least a minimum amount ofstimulation (i.e., defined as an amount below which stimulation has noeffect) is always provided to the user within the time window. Forexample, a minimum duration and/or duty cycle of tDCS can always beprovided to the user within the time window so that the electricalstimulation treatment provided to the user always has a measureableeffect on the user's neural plasticity. As such, Blocks S130-S150 canenable transmission of a limited amount of electrical stimulationtreatment to the user in a manner that automatically provides the userwith electrical stimulation when the user needs electrical stimulationthe most, and in a manner that has a measureable effect on the user'sneurological condition. Again, in some variations, Blocks S130-S150 cansubstantially omit modulating the stimulation session according to amaximum limit constraint, in relation to interruptions to the sessiondue to impedance-related factors.

Similar to methods described above, transitioning back to thestimulation session can include implementation of a second DACmanagement component that appropriately ramps up the current for thestimulation to a desired level. However, stimulation can alternativelybe resumed in Block S150 without ramping or otherwise implementing asecond DAC management component.

In an example application, as shown in FIG. 2, once the impedance fallsbelow a threshold impedance value during the first impedance monitoringstate (after, the electrical stimulation device can enter an idlingstate (e.g., a “Good to go” state); however, if impedance rises, theelectrical stimulation device can enter a waiting state (e.g., a“suspend stimulation” state). Once a below threshold impedance value(e.g., 12 kΩ) along the stimulation path is sustained for a certainduration of time, the electrical stimulation device can be transitionedback to the stimulation regime, resuming the stimulation sessionaccording to the waveform definition at the point of interruption.

In the example, the electrical stimulation device implements a secondDAC management component to ramp up the current for stimulationaccording to a programmed maximum ramp slope (e.g., 0.3 mA per second)rather than immediately setting the attempted current value to the valueof the current when stimulation was interrupted, according to thewaveform definition. As shown in FIG. 2, as stimulation proceeds,impedance typically (but not necessarily) drops gradually over thecourse of stimulation due to electrochemical reactions and biologicaleffects. Stimulation can then terminate normally according to thewaveform definition, if no other current deviations or impedancedeviations are experienced. Alternatively, the method 100 can repeatimplementation of Blocks S130-S150 if another deviation in current orimpedance is experienced.

In variations, the method 100 can omit or rearrange blocks describedabove, based upon situation or status of the electrical stimulationdevice. For instance, the method 100 can omit implementing the firstimpedance monitoring stage after stimulation has been interrupted due tohigh impedance, and instead implement other methods of detecting changesin position of the electrical stimulation device relative to the body ofthe user, and repositioning the electrical stimulation device. In onesuch example, the electrical stimulation device can cooperate with aposition determining device (e.g., optical system, near fieldcommunication system, etc.) that detects and stores the position of theelectrical stimulation device in association with proper impedancecharacteristics along the stimulation path(s) and tracks the relativeposition between the electrical stimulation device and the positiondetermining position during stimulation. Then, if the position changes,the controller can be configured to guide readjustment of the electricalstimulation device's position, according to the position determiningdevice, until the correct position is reachieved. Alternatively, theelectrical stimulation device can be configured to deliver additionalelectrolyte solution (e.g., saline), to or through the electrodes in anattempt to reduce impedance along the stimulation path(s). However,other variations of the method 100 can additionally or alternativelyinclude any other suitable blocks or steps, rearrange blocks, or omitportions of blocks.

In one example of an optical position determining system, one or morecameras on the controller 220 can be used used to capture images orvideo of the electrical stimulation device located on or near the head.These images or video can include fiducial points located on theelectrical stimulation device, such as circular features, dots, joints,angles, colored patches, and/or other features amenable toidentification using techniques known in the art of computer vision.These images or video can also include identifiable points on the head,such as eyes, nose, ears, vertex, inion, preauricular point, and/orothers, amenable to identification using techniques known in the art ofcomputer vision and facial recognition. The controller 220 can create aninternal virtual model of actual head and electrical stimulation devicepositions, and calculate an optimal position for the electricalstimulation device based on intended use, intended placement, orinformation specific to that user and/or informed by functionalneurophysiological measurements such as EMG potentials triggered bytranscranial magnetic stimulation (TMS). The controller 220 can use thismodel of actual position and optimal position to guide the user inreadjustment of the electrical stimulation device's position.

As a person skilled in the field of biosignals will recognize from theprevious detailed description and from the figures and claims,modifications and changes can be made to the preferred embodiments ofthe method 100 without departing from the scope of the method 100.

2. System

As shown in FIGS. 6A and 6B, an embodiment of a system 200 for providingelectrical stimulation to a user can include one or more of: anelectrical stimulation device 210 configured to provide a stimulationsession to the user and monitor impedance characteristics alongstimulation path(s) associated with the stimulation session; and acontroller 220 coupled to the electrical stimulation device, wherein thecontroller is configured to control provision and modulation of thestimulation session to the user according to a waveform definition andthe monitored impedance characteristics. The system 200 is preferablyconfigured to perform an embodiment of the method 100 described above,but can additionally or alternatively be configured to perform any othersuitable method, including methods described in one or more of: U.S.application Ser. No. 14/470,683 titled “Electrode System for ElectricalStimulation” and filed on 27, Aug. 2014, U.S. application Ser. No.14/470,747 titled “Method and System for Providing ElectricalStimulation to a User”; U.S. App. No. 62/292,511 titled “StimulationSystem and Method” and filed on 8, Feb. 2016; U.S. App. No. 62/442,350titled “Stimulation System and Method” and filed on 4, Jan. 2017; U.S.application Ser. No. 14/878,647 titled “Electrode System for ElectricalStimulation” and filed on 8, Oct. 2015; U.S. application Ser. No.15/059,095 titled “Method and System for Providing ElectricalStimulation to a User” and filed on2, Mar. 2016; and U.S. applicationSer. No. 15/335,240 titled “Electrode Positioning System and Method” andfiled on 26, Oct. 2016.

The system 200 preferably includes embodiments, variations, and examplesof system elements as described in U.S. App. No. 62/292,511 filed 8,Feb. 2016 and titled “Stimulation System and Method” and U.S.Provisional Application Ser. No. 62/442,350 filed 4, Jan. 2017 andtitled “Stimulation System and Method”, which are each incorporatedherein in their entireties by this reference. The system 200 canadditionally or alternatively include elements described in one or moreof: U.S. application Ser. No. 14/470,683 titled “Electrode System forElectrical Stimulation” and filed on 27, Aug. 2014, U.S. applicationSer. No. 14/470,747 titled “Method and System for Providing ElectricalStimulation to a User”; U.S. App. No. 62/292,511 titled “StimulationSystem and Method” and filed on 8, Feb. 2016; U.S. App. No. 62/442,350titled “Stimulation System and Method” and filed on 4, Jan. 2017; U.S.application Ser. No. 14/878,647 titled “Electrode System for ElectricalStimulation” and filed on 8, Oct. 2015; U.S. application Ser. No.15/059,095 titled “Method and System for Providing ElectricalStimulation to a User” and filed on 2, Mar. 2016; and U.S. applicationSer. No. 15/335,240 titled “Electrode Positioning System and Method” andfiled on 26, Oct. 2016.

The electrical stimulation device 210 is preferably in communicationwith the controller 220, and functions to deliver electrical stimulationto a user through a set of electrodes 211. The electrical stimulationdevice 210 is preferably configured to generate and provide TEStreatments, but can additionally or alternatively be configured toprovide any other suitable electrical stimulation treatment, asdescribed in relation to the method(s) above. Preferably, the electricalstimulation device 210 comprises an electrode array 221, but canalternatively comprise a single electrode. The controller 220 isoperable to output a current value based upon the set current outputaccording to the waveform definition, wherein the output value is setfrom a computing system (e.g., central processing unit, microcontroller,etc.).

In an example, as shown in FIGS. 7A and 7B, and in relation to impedancemeasurements, the electrical stimulation device 210 and the controller220 can include an electronics configuration that supports one or moreof the following: a current limiting resistor 221 that limits the outputcurrent regardless of any faults or errors in software/the system,wherein the value of the current limiting resistor determines themaximum allowable current output; a first node 222 at which voltage canbe measured in order to sense current through the stimulation path(e.g., from STIM_OUT to STIM_IN/ISENSE, with a minimum 14 bits ofresolution, 10 times per second), wherein the current value is used witha voltage measurement to calculate impedance; a second node 223 that isused to measure voltage (e.g., with a minimum 14 bits of resolution, 10times a second), wherein the voltage value is used with the currentmeasurement from 222 to calculate impedance; and a voltage controlledcurrent output 224 that can route current through a normally-openswitching device (e.g., an analog switch solid state relay), in serieswith the electrodes to the user, an example of which is shown in FIG.7B. In this example, the stimulation path is from STIM_OUT toSTIM_IN/ISENSE; however, the stimulation path can additionally oralternatively be defined in any other suitable manner (e.g., throughanother ground path).

In embodiments such as the example shown in FIG. 7A, the output stage226 can be referenced not to ground, but to a 1V reference 227, so thatthe output stage 226 can apply a small negative voltage across thestimulation path if necessary, without reconfiguring any multiplexer orswitches after the output stage, in addition to being able to apply anormal full-scale positive voltage. The small negative voltage (in thisexample, <1V) can be produced by the output stage 226, when necessary,to overcome electrochemical polarization at the electrode-to-electrolyteinterface. For example, if the output stage 226 is governed by the DACto hold a constant zero current across the user's body region, but ifelectrode polarization has occurred (e.g., such that a non-zero currentwould flow if the output stage 226 were to apply zero voltage), theoutput stage 226 with the reference 227 can be operable to apply a smallnegative voltage to maintain the constant zero current.

The method 100 and system 200 of the preferred embodiment and variationsthereof can be embodied and/or implemented at least in part as a machineconfigured to receive a computer-readable medium storingcomputer-readable instructions. The instructions are preferably executedby computer-executable components preferably integrated with the system200 and one or more portions of the processor and/or a controller. Thecomputer-readable medium can be stored in the cloud and/or on anysuitable computer-readable media such as RAMs, ROMs, flash memory,EEPROMs, optical devices (CD or DVD), hard drives, floppy drives, or anysuitable device. The computer-executable component is preferably ageneral or application specific processor, but any suitable dedicatedhardware or hardware/firmware combination device can alternatively oradditionally execute the instructions.

The FIGURES illustrate the architecture, functionality and operation ofpossible implementations of systems, methods and computer programproducts according to preferred embodiments, example configurations, andvariations thereof. In this regard, each block in the flowchart or blockdiagrams may represent a module, segment, or portion of code, whichcomprises one or more executable instructions for implementing thespecified logical function(s). It should also be noted that, in somealternative implementations, the functions noted in the block can occurout of the order noted in the FIGURES. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently, or theblocks may sometimes be executed in the reverse order, depending uponthe functionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

As a person skilled in the field of neuromodulation will recognize fromthe previous detailed description and from the figures and claims,modifications and changes can be made to the preferred embodiments ofthe invention without departing from the scope of this invention definedin the following claims.

We claim:
 1. A method for providing electrical stimulation to a userwith an electrical stimulation device in communication with acontroller, the electrical stimulation device configured to be arrangedat a head region of the user, the method comprising: upon activation ofthe electrical stimulation device, transitioning the electricalstimulation device from a baseline state to a first impedance monitoringstate; during the first impedance monitoring state, determining a firstimpedance value of the electrical stimulation device; in response todetermining that the first impedance value does not satisfy a firstimpedance criterion, guiding, with the controller, an adjustment of aposition of the electrical stimulation device at the head region of theuser until the first impedance criterion is satisfied, wherein guiding,with the controller, the adjustment of the position of the electricalstimulation device at the head region of the user comprises visuallyguiding the user, with a display of the controller, to adjust theposition of a head-mountable portion of the electrical stimulationdevice; in response to determining that the first impedance value doessatisfy the first impedance criterion, transitioning the electricalstimulation device from the first impedance monitoring state to astimulation regime comprising a second monitoring state having a secondcriterion, wherein the stimulation regime provides an electricalstimulation session, according to a set of waveform features, to theuser, wherein transitioning the electrical stimulation device to thestimulation regime comprises ramping up the stimulation regime; and inresponse to detecting that the second criterion is not satisfied,transitioning the electrical stimulation device from the stimulationregime to the first impedance monitoring state.
 2. The method of claim1, wherein guiding the adjustment of a position of the electricalstimulation device comprises guiding an adjustment of at least one of aset of electrodes of the electrical stimulation device in a directiontangential to a scalp surface of the head region.
 3. The method of claim1, wherein guiding the user with the controller comprises guiding theuser with an application executing on a mobile device associated withthe user and communicatively coupled to the electrical stimulationdevice, the mobile device comprising the controller.
 4. The method ofclaim 3, wherein guiding the user with the controller comprisesrendering, at a display of the mobile computing device, a representationof the head-mountable portion of the electrical stimulation device and arepresentation of a set of electrodes of the electrical stimulationdevice relative to the head-mountable portion.
 5. The method of claim 4,wherein the set of electrodes are reversibly coupled to thehead-mountable portion.
 6. The method of claim 3, wherein guiding theuser with the controller further comprises providing, through theapplication, a notification for the user to deliver a solution to theset of electrodes configured to reduce an impedance along a stimulationpath.
 7. The method of claim 1, wherein transitioning to the firstimpedance monitoring state comprises producing a set of biphasic currentpulses at the electrical stimulation device.
 8. The method of claim 7,wherein implementing the first impedance criterion comprises comparingimpedance measurements across a subset of the set of biphasic currentpulses to a threshold impedance value, and transitioning the electricalstimulation device from the first impedance monitoring state to thestimulation regime if impedance measurements are below the thresholdimpedance value for a predetermined duration of time.
 9. The method ofclaim 1, wherein transitioning the electrical stimulation device fromthe stimulation regime to the first impedance monitoring state isperformed at a first time point, wherein the method further comprises:in response to detecting that a third impedance criterion of the firstimpedance monitoring state is satisfied, transitioning the electricalstimulation device from the first impedance monitoring state to thestimulation regime at a second time point.
 10. The method of claim 9,wherein implementing the first impedance monitoring state includesimplementing a two-part hysteresis criterion for reducing cyclingbetween at least one of the first impedance monitoring state, the secondmonitoring state, and the stimulation regime.
 11. The method of claim 9,wherein the first impedance monitoring state comprises measuringimpedance with the electrical stimulation device according to a firsttechnique, and wherein the second monitoring state comprises measuringimpedance with the electrical stimulation device according to a secondtechnique that is different from the first technique.
 12. The method ofclaim 9, wherein the first impedance criterion of the first impedancemonitoring state has a first impedance value, and wherein the thirdimpedance criterion of the first impedance monitoring state has a secondimpedance value greater than the first impedance value.
 13. A method forproviding electrical stimulation to a user with an electricalstimulation device in communication with a controller, the electricalstimulation device configured to be arranged at a head region of theuser, the method comprising: upon activation of the electricalstimulation device, transitioning the electrical stimulation device froma baseline state to a first impedance monitoring state; during the firstimpedance monitoring state, determining a first impedance value of theelectrical stimulation device; in an event that the first impedancevalue does not satisfy a first impedance criterion, guiding, with thecontroller, a modification of a set of electrodes of the electricalstimulation device at the head region of the user until the firstimpedance criterion is satisfied, wherein guiding, with the controller,the modification of the electrical stimulation device at the head regionof the user comprises visually guiding the user with a display of thecontroller; and in response to detecting satisfaction of the firstimpedance criterion, transitioning the electrical stimulation devicefrom the first impedance monitoring state to a stimulation regimecomprising a second monitoring state having a second criterion, whereinthe stimulation regime provides an electrical stimulation session,according to a set of waveform features, to the user, whereintransitioning the electrical stimulation device to the stimulationregime comprises ramping up the stimulation regime; and in response todetecting that the second criterion is not satisfied, transitioning theelectrical stimulation device from the stimulation regime to the firstimpedance monitoring state.
 14. The method of claim 13, wherein guiding,with the controller, a modification of the set of electrodes comprisesguiding the user, with a display of the controller, an adjustment of aposition of at least one of the set of electrodes the electricalstimulation device at the head region of the user until the firstimpedance criterion is satisfied.
 15. The method of claim 13, whereinguiding the user with the controller comprises providing, through theapplication, a notification for the user to deliver a solution to theset of electrodes configured to reduce an impedance along a stimulationpath.
 16. The method of claim 13, wherein transitioning the electricalstimulation device form the stimulation regime to the first impedancemonitoring state is performed at a first time point, wherein the methodfurther comprises: in response to detecting that a third impedancecriterion of the first impedance monitoring state is satisfied,transitioning the electrical stimulation device from the first impedancemonitoring state to the stimulation regime at a second time point. 17.The method of claim 16, wherein implementing the first impedancemonitoring state includes implementing a two-part hysteresis criterionfor reducing cycling between at least one of the first impedancemonitoring state, the second monitoring state, and the stimulationregime.
 18. The method of claim 16, wherein the first impedancecriterion of the first impedance monitoring state has a first impedancevalue, and wherein the third impedance criterion of the first impedancemonitoring state has a second impedance value greater than the firstimpedance value.
 19. The method of claim 13, wherein transitioning tothe first impedance monitoring state comprises producing a set ofbiphasic current pulses at the electrical stimulation device.
 20. Themethod of claim 19, wherein implementing the first impedance criterioncomprises comparing impedance measurements across a subset of the set ofbiphasic current pulses to a threshold impedance value, andtransitioning the electrical stimulation device from the first impedancemonitoring state to the stimulation regime if impedance measurements arebelow the threshold impedance value for a predetermined duration oftime.